As the cost of fuels and energy in all forms continues to rise with rapid depletion of supplies, the necessity for energy conservation becomes increasingly apparent and in those industries where operating costs rest heavily on the price of fuel, it is absolutely essential that significant improvements be made in terms of fuel economy. The realization of such improvements will have important effects on the economic health of the nation which has become increasingly dependent upon foreign sources of fuel.
The metal processing industries are heavily involved in this problem because of the large volumes of fuels they consume, and aluminum remelt operations, with which this invention is concerned, provide a significant opportunity for improved utilization of energy resources.
In a typical remelt furnace the exhausted flue gases carry with them large quantities of unused energy in the form of heat. The primary object of this invention is to put this wasted heat energy to work in a preheat stage and thereby to reduce the total amount of energy required for the processing of a given weight of aluminum.
It is estimated that under ideal furnace operating conditions, preheating can produce as much as an 18% to 20% heat rate improvement; in some of the older and less efficient furnace installations, a somewhat higher BTU recovery can be realized even though the percentage in heat rate improvement may be somewhat lower.
Due to the attendant shortening of the remelt cycle, the net reduction in heat required per pound of melt approaches 25% to 32%, undiscounted for non-firing periods.
An additional benefit to be realized through preheating is the increased furnace capacity or throughput per day which results from the reduction in the required melting time per charge. Throughput improvements as high as 55% are possible at a 1450.degree. F. tapping temperature.